Automated data storage libraries typically store cartridges of tape or of optical disks and are secondary to disk storage for the storage of data for data processing systems. Disk storage is relatively high in cost and therefore limited in capacity. The function of data storage libraries is to store data which is not constantly required, but is on line and available quickly when needed. Data storage libraries therefore must be efficient in maximizing capacity in limited space while accessing the stored data quickly.
Typical automated data storage libraries have stationary columns of cells for storing data cartridges. Pickers either move linearly or rotate to access the columns. Some libraries have been contemplated which rotate a cylinder of columns of cells while maintaining the picker stationary. The configurations typically have a single row of columns of cells, or, in a few instances, a row on either side of the picker. Capacity may be increased by increasing the length of the rows of cells. However, the length of the rows is limited by the designed maximum length of time allowed for accessing the data cartridges.
Thus, it is desirable to maximize storage capacity and yet be as compact as possible to avoid excessive data access times.